The present invention relates generally to the fastener art and, more particularly, to improved gear-headed fasteners drivable from a substantially perpendicular direction by a rotary drive tool.
It is often desirable to drive a threaded fastener from a direction perpendicular to its axis, especially when space in the area of the fastener head is restricted. One troublesome case is the joining of furniture members or stair rails so that the fastener is contained with the objects being joined and is hidden from view. Even if the fastener can be positioned within a blind opening in one of the objects, it is difficult to tighten the fastener unless a large open area is provided near its head. Currently available fasteners and fastener drive tools are generally unsatisfactory for this purpose.
Prior tools for tightening fasteners from a direction perpendicular to the fastener axis include open end, box end and socket wrenches. However, such wrenches are unsuitable for use in many cases because open space is required to: (1) insert the fastener linearly into the clearance opening along its full length; (2) fit the wrench over the head of the fastener in the unthreaded condition; and (3) swing the tool back and forth within a perpendicular plane in a tightening sequence. The operating tool must also be repeatedly engaged, disengaged and reengaged with the head of the fastener if a ratchet device is not used.
An improved form of fastener is described in Danish Pat. No. 63979 and Swedish Pat. No. 124018. The fastener disclosed therein has a plurality of gear teeth projecting radially from its shank to form a worm wheel engageable with a worm gear of a rotary drive tool. The fastener can be driven from a direction 90 degrees to its axis, but requires a substantial amount of open space adjacent to the gear teeth because the axis of the drive tool is displaced from the axis of the fastener and the tool has laterally projecting prongs which must engage the fastener.
One form of attaching hardware designed specifically for stair rails and furniture members is a "hanger bolt" having a wood screw shank at one end and a machine screw shank at the other end. The wood screw shank is driven into one object and the machine screw shank projects through a clearance opening in another object, such that the end of the machine screw thread is accessible through an access hole at right angles to the clearance hole. Fastening is completed by a star nut introduced into the access hole and tightened onto the machine screw shank by repeatedly forcing a screwdriver against the points of the star. This is a laborious operation and requires that the objects be assembled progressively, using whatever additional space is required to accommodate the length of the screw thread. Objects cannot be assembled by this method within their combined length.
As a result of the difficulties encountered in attaching objects by the above described methods, carpenters assembling stair rails often discard traditional fasteners and resort to toe-nailing the rails together or to the newel posts supporting them, and gluing the rails together. This makeshift alternative is unsightly and inexact, and often results in an unsafe assembly.
Therefore, it is desirable in many applications to provide an apparatus for securely fastening two objects together within their combined length using a drive tool extending through a restricted access opening in one of the objects and directed at right angles to the fastener axis.